Undergravel filters, particularly those having a number of flow-through openings, are commonly used in many aquariums. During use of undergravel filters, water is drawn downward through the openings due to suction created by airlifts or powerheads which are commonly arranged at one or two corners of the filter. After passing through the openings in the filter, the water is drawn under the filter until it randomly reaches a lift tube hole which allows the water to be drawn upward through a lift tube. Undergravel filters of this type are commonly covered with gravel to provide both mechanical and biological filtration.
Several problems exist with undergravel filters which are currently commercially available. First, water which is drawn through the openings follows a random, non-structured path under the filter before it reaches a lift tube. Consequently, water is preferably drawn through the filter near a lift tube, while water is drawn through the filter far from the lift tube only as the closer tube becomes clogged with debris. This randomness in drawing water through the lift tube leads to uneven filtration throughout the entire aquarium. In addition, fish frequently dig and move the gravel. This often exposes the openings in the filter directly to the water and allows water to pass through the openings, creating a path of least resistance and reducing the efficiency of the remainder of the filter.
In light of the problems with currently available undergravel filters, it would be advantageous to provide an undergravel filter which would address these problems. Consequently, it is an object of the present invention to provide an undergravel filter which will lead to even filtration over the surface of the entire filter and, in a preferred embodiment, will prevent fish from digging and moving gravel.